The invention relates to steerable pushing means for a combination of a pusher tug with barges, which combination consists of a pusher tug with at least one barge unit, whereby each unit may comprise one, two or more barges coupled alongside each other, and the pusher tug has at least one propelling mechanism, and the combination comprises at least one steerable pushing means, consisting of a horizontal support frame connected to the stem, which support frame carries and guides a pushing beam pivotable around a vertical shaft and positioned perpendicular to the centerline of the combination and whereby for steering purposes at both sides of the pivot shaft a jack or similar extendable or retractable means is installed between the support frame and the pushing beam.
Sailing with combinations of a pusher tug and barges on rivers, as for instance the river Rhine, with many ship movement and a number of relatively sharp curves, not only requires good steersmanship, but besides that is also influenced by the other ship movements on the waterway. The result thereof is that the supervisors of these waterways have set limits, not only to the width, but especially to the length of such combinations. On the river Rhine for instance, combinations with up to two times two barges are allowed, which means a unit consisting of two barges coupled board to board alongside each other followed by a similar unit with the pusher tug thereafter at the center line. Notwithstanding the relatively low water depth, the pushing tugs are capable to deliver sufficient propelling power for transporting combinations of three times two barges, that means three units, or even more. However, the manoeuverability of such a stiff combination is doubtful. In such a combination all the barges are mutually stiff coupled to each other using crosswires, longitudinal wires and tranverse wires. Also the pusher tug is stiff coupled behind the barges. By means of an additional front rudder it is possible to improve the steerability in some way and by means of a front screw which may act to the starboard side or to the portside a stronger improvement is possible. The object of the invention is to realise with very simple means a much more important contribution to the improvement of the steerability of combinations of this type, such that running longer combinations consisting of five or six barges in three units will become a possibility.
Steerable pushing means as described in the heading are known from the U.S. Pat. No. 3,035,537. By means of the system described in said publication a pusher tug is stiff but also movable coupled to a barge. Said coupling is realised by means of pivot pins at the barge side, which barge should comprise therefore separate connecting elements. The described steerable pushing means are intended for light applications as appears from the construction and the examples. Using a similar construction in a combination of a pusher tug and barges with units of thousands of tons in the rough professional transport business on rivers as the river Rhine for transporting for instance coal and ore seems out of the question. One of the problems thereby is without doubt the coupling of the described pushing means to the barges and the decoupling therefrom, whereby furthermore the vulnerability of the connecting means onto the stern of the barges is unacceptable for the intended application.